This paper introduces a method to compare direct mechanisms based on their vulnerability to manipulation or deviation from truthful reporting. We explore the following idea: if a player can manipulate mechanism psi whenever some player can manipulate mechanism phi, then psi is more manipulable than phi. Our notion generates a partial ordering on mechanisms based on their degree of manipulability. We illustrate the concept by comparing several well-known mechanisms in the matching and auction literature. The applications include comparisons between stable matching mechanisms, school choice mechanisms, auctions for internet advertising, and multi-unit auctions.
This talk is based on joint work with Tayfun Sonmez of Boston College.